I absolutely forbid any such outrage,” George Bernard Shaw said in 1948 when asked about turning his play Pygmalion into a musical (he was similarly opposed to having his plays become movies. Even after Shaw was dead, Cole Porter, Noel Coward, and Rodgers and Hammerstein all reportedly declined offers to attempt a musical about how phonetics professor Henry Higgins transforms cockney flower girl Eliza Doolittle into an English lady. Alan Jay Lerner and Frederick Loewe finally took up the challenge, and on March 15, 1956, their My Fair Lady opened triumphantly on Broadway. Recalls Kitty Carlisle Hart, then married to the show’s director, Moss Hart: ”In the middle of ‘The Rain in Spain,’ it was as if the entire audience had taken a concerted deep breath and was two feet off their seats with delight.”

The show, propelled by the radiant pairing of Julie Andrews and Rex Harrison, broke numerous records. Its 2,717 performances made My Fair Lady the Great White Way’s longest-running musical until Fiddler on the Roof (and later A Chorus Line). And the cast album eclipsed South Pacific to become the best-selling Broadway record in history at the time.

Yet Julie and Rex almost didn’t make the cast. Mary Martin was offered the part of Eliza first but turned it down because she didn’t like the initial score. Harrison had never done a musical and wasn’t confident about his suitability. ”It’s a big step, and a big risk to take on a musical when… you can’t sing,” he wrote in his autobiography, A Damned Serious Business, published posthumously last month by Bantam Books. Undaunted, Lerner and Loewe updated the ”patter” song: Harrison spoke the lyrics to songs like ”I’ve Grown Accustomed to Her Face.”

Harrison re-created Higgins in the 1964 movie version, but Andrews was passed over for popular film star Audrey Hepburn, whose songs were dubbed by Marni Nixon. Andrews soon got revenge. Harrison won the Best Actor Oscar that year — and Andrews won Best Actress for Mary Poppins, which sent her on to further fame as Maria in the film The Sound of Music.

TIME CAPSULE: March 15, 1956 TV viewers were figuring out The $64,000 Question while Sen. John F. Kennedy’s Profiles in Courage made the nonfiction bestseller list. At the movies, Frank Sinatra scored as a drug addict in The Man With the Golden Arm; Nelson Riddle’s short-lived hit, ”Lisbon Antigua,” topped the record charts.